A vane pump includes a rotor that receives vanes, a cam ring that has an inner circumferential cam face with which tip portions of the vanes are brought into sliding contact, and a side plate that is in sliding contact with one end side of the rotor in the axial direction. A discharge port is formed on the side plate, and this discharge port is for guiding working fluid discharged from pump chambers that are defined by the rotor, the cam ring, and the adjacent vanes.
JP2001-248569A discloses that a notch, which is a groove, is formed on a side plate so as to extend from an opening portion of a discharge port in the direction opposite to the rotating direction of a rotor. With such a configuration, when the rotor is rotated to supply/discharge the working fluid, the pump chamber is opened to the notch before opening to the discharge port, and thereby, the high-pressure working fluid is supplied through the notch from the discharge port to the pump chamber that is positioned rearward in the rotating direction. Thus, because it is possible to gradually increase the pressure in the pump chamber before the pump chamber is pressurized to a high pressure, it is possible to suppress rapid pressure variation in the pump chamber.